Adaptive phenotypes and the barrier to introgression between ecotypes

Lead Research Organisation: University of Sheffield
Department Name: Animal and Plant Sciences

Abstract

Even though is is now more than 150 years since Darwin's famous book, there is still much to learn about the origin of new species. The problem is fundamentally one of genetics because species are characterised by their inability to exchange genes with other species. This 'reproductive isolation' can be due to chance changes that reduce the fitness of hybrid offspring, to adaptation to different environments or to changes in habitat choice and mating behaviour that prevent the species from interbreeding. In general, it is not known which type of reproductive isolation appears first or how the different types come together to produce completely isolated species.

In this project, we propose to study two forms of winkle, a type of snail that lives on rocky coasts. One form is adapted to wave-exposed environments without crab predators (W) and the other to sheltered environments with any crabs (C). Where these environments meet, the different types can interbreed although they prefer to mate with their own type. On the Swedish coast there are many contact points between the two types which we can use as replicates. In each contact, we will examine genetic markers throughout the winkles' genomes. For some parts of the genome, we expect to see sharp changes close to the environmental boundary. These regions are experiencing partial reproductive isolation. For other parts of the genome, we expect to see little or no change because they are not connected to any traits involved in reproductive isolation. Comparing mutliple contacts gives us a very powerful way to find the parts of the genome that experience the strongest reproductive isolation.

The next question will be why each of these regions experiences reproductive isolation. To answer this question, we will determine several important characteristics of each winkle that we study genetically. The characteristics include shell size and shape, and the 'boldness' of the snail (its willingness to come out of its shell). The characters are all associated with a trade-off between adaptation to wave exposure and adaptation to crab predation. We will also measure the preference of males for different sized females and the reproductive success of females (number and development of embryos). We can then test whether genes in the regions that experience isolation contribute to variation in these important traits and so whether reproductive isolation is due mainly to adaptation, to offspring fitness or to mate choice. Some regions may not be associated with any of these traits and these will be very interesting, pointing to forms of isolation that we have not studied to date.

This will be one of the first studies to find isolated regions of the genome and to explain the sources of isolation. Therefore, it will take us a step closer to solving Darwin's 'mystery of mysteries', the origin of species.

Planned Impact

While the primary beneficiaries of this research are academic scientists interested in evolutionary processes, we see two other groups of beneficiaries:

1. Policy makers and practitioners concerned with the management of biological diversity in the face of climate change. The effectiveness of management measures will be enhanced by better understanding of the process of adaptation to changing environments (both spatially and temporally), the nature of differentiation among populations and the nature of species. We propose to address this group by summarising our results and their implications in a report suitable for biodiversity management professionals, primarily aimed at a senior level in Natural England, and by an article aimed at a wider audience in a periodical such as British Wildlife.

2. The public, whose interest in biological diversity and evolution is clear but whose knowledge and undertanding of evolutionary processes is generally quite limited. We will exploit the fact that our field sites in the UK include popular holiday destinations. We will provide intepretation and demonstrations at appropriate sites where our previous experience suggest that it is easy to attract attention.

Publications

10 25 50
 
Description Analysis of phenotypic and genetic change across sharp boundaries between different habitat types has revealed new information on the genetic basis of local adaptation.
Exploitation Route Our findings contribute to understanding of evolutionary change, especially speciation.
Sectors Environment

 
Description We have contributed to the public understanding of science through displays and activities that use local adaptation in snails to illustrate evolutionary processes.
First Year Of Impact 2016
Sector Other
Impact Types Societal

 
Description SciLife National Biodiversity projects
Amount 618,750 kr (SEK)
Organisation Science for Life Laboratory 
Department National Genomics Infrastructure
Sector Academic/University
Country Sweden
Start 06/2015 
 
Description Waernska Guest Professorship
Amount 500,000 kr (SEK)
Organisation University of Gothenburg 
Sector Academic/University
Country Sweden
Start 06/2014 
End 06/2015
 
Description CeMEB 
Organisation University of Montana
Department Marine Sciences
Country United States 
Sector Academic/University 
PI Contribution Expertise in population genetics/genomics. Joint working.
Collaborator Contribution Field facilities. System expertise. Joint working.
Impact Tage Erlander, Waernska and SciLife funding opportunities relied on this partnership. Multiple publications also relied on the interaction.
Start Year 2009